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heat. Ten or twelve dozen of hats are im-merfed by a proper contrivance into the liquidfor about an hour and a half, then taken outand aired, and another fet immediately immerfedfor the like time. Each fet is dipped and airedalternately for eight times, the bath being oc-cafionally refreffied by more of the ingredients.The verdigris is found by experience to beelfential to the beauty of the dye.

It is a much more difficult operation to fix apermanent black on linen and cotton, whichwill ftand waffiing with foap and long expofureto the air. The proceffes that fucceed on wooldo not anfwer well here, the black being veryliable to degenerate to a rufty brown.

Linen or linen thread is generally firft bluedwith indigo and then receives a mordant ofalum, after which it is palled through a bath ofgalls or logwood, or alder, and blackened withthe iron folution, for which a variety of pre-cedes are given.

A fine durable black on cotton is of ftillmore confequence in the prefent immenfe tradeof printed cottons than on linen, and muchpains has been taken to equal the excellent fallblack given to cotton goods in the Eaft Indies,the procefs for which is not known, unlefs itbe with the anacardium or other native vege-table juices. For many years a kind of acetiteof iron has been ufed very largely in Englandas a fubftitute for the fulphat in the black dye,and alfo partly as a fubftantive colour, by whichalone many ufeful fhades of buff, nankeen, andother dyes are given. This acetite is made bymacerating refufe pieces of iron in four beer,vinegar, elder-berries, and other fubftances thatafford the vegetable acids and produce in timea very ftrong uncryltallizable high-coloured fo-lution. Of late years too the pyroligneous acid(obtained from the diftillation of wood in mak-ing the beft charcoal for gunpowder) and theempyreumatic acid of tar have been ufed veryextenfively in calico-printing for fimilar pur-pofes and with very compleat fuccefs, but theprecife mode of application is kept fecret. Itappears that galls or fimilar vegetable matterare not required with this preparation, but theplace Js fupplied with madder, which with adeep iron ground may be made to give a verydark purple-brown hardly diftinguiffiable fromblack.

Since cotton and linen, which are of vege-table origin, have naturally lefs affinity withcolouring matter than wool and animal matters,dyers have been in the habit in many parts of

the world of impregnating linen and efpeciallycotton with many compound mordants, theunited effeft of which is certainly in many in-ftances to enable them to take and retain colourswith much more perfection than any Amplerprocefs could obtain. Sometimes thefe mor-dants are animal glues, animal oils, dung, &c.and it has been very happily conjectured thatthe great advantage of thefe is in fome degreeto animalize the vegetable fibre, as it were, andthus in point of affinity with colouring matterto bring it more on a level with wool, filk, andthe natural animal fibres. The fine turkey redof madder fixed on cotton by a very complicatedprocefs, is a ftriking inftance of the ufe of thefecompound mordants, as will be afterwards men-tioned. The following procefs for dyeing linenand cotton of a fine durable black is given byMr. Vogler, an eminent practical artift, inwhich animal glue is ufed as a mordant, to-gether with a folution of lead, which laft feemsto have a ftrong affinity for the materials ofwhich the black dye is compofed.

Mix in a large bottle * a quart of foft waterwith 2 or 24 ounces of common aquafortis, andthrow in from 2 to 3 ounces of litharge. Setthe bottle in a warm place frequently fhakingit, till a folution is made, which when ufedfhould be poured off clear from the fediment.In this dilute nitrated lead firft foak the linenor cotton thread (without heat) for ten or twelvehours, then take it out, waffi it and wring itwell. Next dip the thread into a moderatelyftrong warm glue water, wring it out but do notwaffi it, and let it dry in the fhade. Next makea decoCtion of ■£ of an ounce of galls in aquart of water, and when they have boiled forten minutes throw in f of an ounce of fait.Then foak the thread therein for feven or eightminutes with a boiling heat, waffi, wring anddry as before. The thread has now a darkyellowiffi grey colour. Afterwards diffolve ■£of an ounce of fulphat of iron with as muchfait in a quart of clean hot water, foak thethread therein for eight or ten hours, afterwhich waffi and dry. The colour is now blackbut is much improved by the following opera-tions. Boil f of an ounce of logwood in aquart of water for ten minutes, after which adda quarter of an ounce of ftarch, and when wellmixed put in the blackened thread or ftuffi andboil for 7 or 8 minutes, after which waffi it mcold water and dry. Laftly, the colour, whichis much improved by the foregoing operation isfixed by the following. Make a bath of one

• Crell’i Annals or Repertory, vol. 8.

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